Gtjxdo foknaca



G. FORNACA Sept. 27, 1927. 1,643,408

PNEUMATIC BUFFER FOR RECIPROCATINGMACHINE MEMBERS Filed Jan. 8, 1927 Fig.1 Fig.2

Patented Sept. 27, 1927.

UNITED STATES PATENT OFFICE.

sumo FORNACA, or'runm, ITALY.

P vEUMATIc BUFFER r03 nEoIPRocA'rING MACHINE MEMBERS.

Application filed .TanuaryB, 1927, Serial No. 159,925, and in Italy January 16, 1926.

It iswell known that somemachine members and more particularly the distributing parts of engines, pumps etc. (valves, slide valves or the like) are operated through the interrelated action of a driving member (cam) and a spring having the purpose of maintaining the moving machine element and its driving member in permanent con tact.

When the reciprocating masses are big-and receive a rapid motion, it is often difficult to proportionate the spring in such a way as to ensure a'regular working without unduly increasing its size or submitting the material to an excessive strain and avoiding all vibrations, which besides causing tedious noises will finally produce the breakage of the spring. moreover necessary to proportionate the spring in such a way as to counterbalance the stresses occurring when the machines work at the highest possible number of turns. so that the charge on the valve tappets will be too high for lower numbers of turns with a useless consumption of energy. Said drawbacks are. removed by the arrangement forming the object of this invention which utilizes instead of the resiliency of a spring, the elasticity of a fluid under pressure, that acts on a piston connected with the member on which the resilient action is to be exerted; the cylinder in which the piston is movable being fed from a tank with pressure fluid through an automatic valve.

By said arrangement it is possible to proportionate exactly the resilient pressure according to the varying speed of the operated member, thus avoiding all the above mentioned disadvantages.

The annexed drawing shows diagrammatically and by way of example a constructional form of the arrangement forming the object of this invention.

Figure 1 shows the arrangement in a first position.

Figure 2 shows the arrangement in a second position.

The machine member 1 (in the example shown a slide valve gear) is operated by a cam 2 acting on a valve tappet 3 and is connected with a piston 4 movable in a cylinder 5. This latter communicates through an automatic valve 6 and a reducing valve 7 with a tank containing pressure fluid (pres sure air'in the case of explosion engines,

steam in the case of steam engines). There- In variablespeed machines it is.

fore, when the piston i is at its lower dead point, the cylinder is filled up with pressure fluld; by suitably choosing the relative value of pressure and piston area it will bev possible to counterbalance the weight of the sliding valve 1 and parts connected therewith .by-means of the fluid pressure, maintaining moreover the. contact between the valvetappet 3 and the cam 2 under the desired pressure during the inactive period.

As soon as the piston l begins itsupward stroke. the valve 6 is closed and the fluid contained in the cylinder is compressed to an extent depending on the value of the starting pressure and volume of the clearances; by determining said values in relation with the masses of the slide valve 1 and parts connected therewith, the cam profile 2 and speed of the machine, it will be possible to maintain a permanent contact between 3 and 2.

During the upward stroke of the piston 4 the cylinder pressure increases according to the known laws of gas or steam compression; during the back stroke'the gas or steam is expanded giving therefore back nearly all the pressure work. If during the cycle small losses of gas occur, at the end of the return stroke the automatic valve 6 will restore the ordinary tank pressure in the cylinder.

This arrangement is substantially different from other known arrangements, in which the constant pressure of gas or steam is used to balance the weight of a part ofthe inertia stress of reciprocating masses, as the action of the gas or steam on the piston, according to this invention, is varied by means of the compression and expansion in such a way as to generate varying stresses according to a law as near as possible to the rule according to which the stresses due to the driving members are varied. Moreover when the speed of the machine is a variable one, this arrangement will make it possible, by acting by hand or through an automatic controlling apparatus upon the reducing valve 7, to proportionate the starting pressure to the speed, in order to have no excessive charge and therefore useless expenditure of energy at a low number of turns and to prevent the separation of the roller from the cam even at the highest speeds.

lVhat I claim is:

1. Pneumatic butter for a reciprocating machine member actuated by means of a cam comprising a piston connected 1" we reciplOO rocating: member, a cylinder for said piston, a tankcontaining a pressure fluid and come. municating With the cylinder through a conduit and an automatic valve opening towards the cylinder and arranged in said conduit,' for obtainingv variable pressures according,

to the displacement of the piston Within said cylinder and such as to maintaina constant contact between said cam and said reciprocating member.

QVPn'eumat1c butter. for a zl'BClPIOCEtUIlg machine member. actuated i by means: of an eccentric, comprisinga piston connected to the reciprocating member, a cylinder tor Silltl PlSllOD, a tank containing a-pressu re fluid and communicating with the cylinder through a conduit and an automatic valve opening towards the cylinder and arranged in said conduit, for obtainingvariable pressures according to the displacement of the piston withinsaid. cylinder and such as to maintain a constant contact betweenv said:

eccentric and said reciprocating.member.

Pneumatic buffer-tor a reciprocating nrachinemember actuated by means of a cam, comprising a PlStOITCODIIBCtQCl to the reciprocating:member a-cylinder for said piston, a tank. containing -a pressure :fiuid and communicating a- With the cylinder through a conduit and an automatic valve opening towards the cylinder andwarrange'd the stresses exerted by the cam at the different speeds.

at: Pneumatic butter-- for a .reciprocating machine. member actuated by means of a cam, comprising a piston connected to the reciprocating 1nember,- a cylinder. for said piston, a tank containing. a pressure fluid and. communicating With the cylinder through a conduit and an automatic valve opening towards thecylinder and arranged in said conduit, for obtaining variable pressures according to the displacement of the piston Within said cylinder andsuchas to maintain a constant-contact between said cam andsaidreciprocating member, and .a reducing valve arranged 111 said conduit to proportionate the pressure on said piston-to the stresses exerted by the cam-at the diiierent speeds, and automatic means for adjusting the reducing Valve according to, the ditierentspeeds.

In testimony whereof I afiix my signature.

GUIDO FORNAGA.. 

